Dou·ble, v. i.
 1. To be increased to twice the sum, number, quantity, length, or value; to increase or grow to twice as much.
    'T is observed in particular nations, that within the space of three hundred years, notwithstanding all casualties, the number of men doubles.   --T. Burnet.
 2. To return upon one's track; to turn and go back over the same ground, or in an opposite direction.
    Doubling and turning like a hunted hare.   --Dryden.
    Doubling and doubling with laborious walk.   --Wordsworth.
 3. To play tricks; to use sleights; to play false.
 What penalty and danger you accrue,
 If you be found to double.   --J. Webster.
 4. Print. To set up a word or words a second time by mistake; to make a doublet.
 To double upon Mil., to inclose between two fires.